1. Field of the Invention
The invention pertains to a piston-cylinder unit with a piston rod protector having a retaining surface which engages a stop surface on the cylinder
2. Description of the Related Art
The piston rod of a piston-cylinder unit, e.g., a vibration damper, should be protected from dirt, because dust and/or moisture can negatively affect the service life of the piston-cylinder unit. For this reason, a piston rod protector, which encloses the piston rod, is very often used. In its simplest form, the piston rod protector consists of a rigid tube, the inside diameter of which is somewhat larger than the cylinder of the vibration damper. An annular gap therefore remains between the cylinder and the inside surface of the piston rod protector, however, so that it is still possible for dirt to intrude.
DE 41 37 447 C2 describes a telescopic shock absorber, which comprises a cap on the end where the piston rod exits; this cap is provided with a circumferential collar. After assembly, the collar fits into a bellows forming one end of the piston rod protector, where the sequence of assembly steps is intended to be automated. U.S. Pat. No. 5,402,868 also describes a piston rod protector, which can be positively connected to a cylindrical tube end cap equipped with stop surfaces.
The problem is that the assembly process is very difficult to automate. When the piston rod protector comes to rest on the retaining surfaces during the inward-threading movement, manual support is often necessary to ensure that the piston rod protector actually does lock onto the stop surfaces. These manual interventions lead to errors or to extra effort.